First thanks for all you do, frequently in the worst weather and
conditions. I am certain everyone appreciates getting their service
restored. Sadly around pittsburgh Duquesne light tends to wait till a
overloaded tranmsformer fries before replacing it. Even one thats
tripped it thermal protection repeatedly:(
Anyhow my question. Before working on what you BELIEVE is a dead line
do you short it just to be on the safe side?
I was told this by a local lineman and just want to confirm. thanks bob
if you do short lines do you occasionally find one thats still
Depending on voltage and proximity either a meter, or tick tracer is used to
verify lines and equipment is non-energized prior to safety grounds being
Safety grounds are not really effective on the secondary side of a low
voltage transformer. At 13,200 volts, there's only a few thousand amps
available. Not nearly enough current to do anything spectacular with the
safety ground (usually 4/0, fine strand) for the short duration that the
current will be available, assuming good contact with the conductors. On the
secondary side of your typical pad mount 200 kva transformer, normal current
phase to ground on the secondary is on the order of 1600 amps continuous.
Available shourt circuit current might be 20,000 amps or more for a while.
Long enough to burn up a safety ground.
Short answer... grounds are not applied until lines are verified dead.
Grounds are occasionally accidentally applied to hot lines. It shouldn't
happen if proper procedures are followed.
theres was a event here a few years ago.
someone made a bad switch throw, a worker walking by a safety ground
got tossed off the tower when the safety ground exploded.
worker got lifeflighted to hospital trauma unit
I'm not a lineman, so I should not answer.
But, if I were dealing with the high voltage before a pole
transformer, I sure as heck would not short it to test.
Thats what test instruments are for. One other thing. There is always
a removable fuse before a transformer, and I have always seen linemen
remove it before working on a transformer. Now if they are working on
the HV wires themselves, there is more of a risk.
Not a lineman.
However, I've also heard that the line guys will short a line to
ground while working on it -- even if it's supposedly disconnected.
I've also heard that if a home owner is found to be back feeding to
the grid, they will disconnect the person from the grid, and it takes
many months to get the guy hooked back up.
Christopher A. Young
You can\'t shout down a troll.
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